Novel form of rimsulfuron, a process for its preparation and use of the same

ABSTRACT

A crystal form of rimsulfuron is provided that exhibits improved solubility and decreased viscosity. Furthermore, a process for its preparation is provided. The novel crystal form is particularly suitable for use in herbicidal compositions and in the control of unwanted plant growth.

This US patent application claims benefit of U.S. patent applicationSer. No. 15/081,362, filed Mar. 25, 2016, which claims the benefit of UKpatent application no. GB1505464.6, filed 30 Mar. 2015, the entirecontents of which are incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present invention relates to a crystal form of1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-pyridylsulfonyl)urea(rimsulfuron), to its preparation processes and to its use inagrochemical preparations.

DESCRIPTION OF RELATED ART

1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-ethylsulfonyl-2-pyridylsulfonyl)urea(rim-sulfuron)is a potent herbicide having high selectivity, high efficiency, lowtoxicity and other desirable attributes. Rimsulfuron has a molecularformula of C₁₄H₁₇N₅O₇S₂. Its chemical structure is:

It is used post-emergence on crops, such as maize and potatoes, againsta variety of annual and perennial grasses and broadleaved weeds. It israther less toxic towards algae and is of generally low toxicity towardsmost other wildlife.

The commercially available rimsulfuron, which is usually manufactured bythe process described in EP0341011 A1, is present in an amorphous state.It has been found that rimsulfuron in amorphous state is highly viscous,which is not suitable for being prepared as compositions or formulationshaving spray equipment cleanout property. Rimsulfuron residues stay inthe spray equipment after spraying. Adequate cleanout may require arinsing procedure that is not only time-consuming but also results inwastewater disposal problems. Therefore, there is a need to provide anovel form of rimsulfuron with increased solubility and decreasedviscosity.

SUMMARY

Accordingly the present invention provides a novel crystalline form ofrimsulfuron, termed “crystal form A”, and a process for its preparationas well as its use in agrochemical compositions. The novel crystallineform A has been advantageously found to have increased solubility,decreased viscosity and improved spray equipment clean-out properties.Accordingly, the invention also provides compositions for controllingundesirable plant growth, such as weeds, comprising the crystal form Aof rimsulfuron on its own, as a mixture with auxiliaries and carriers,and as a mixture with other active compounds. The use of the crystalform A of rimsulfuron in the control of undesired plant growth and amethod for the same are also provided by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an X-ray powder diffractogram of a crystal form A ofrimsulfuron;

FIG. 2 is an IR spectrum of the crystal form A of rimsulfuron; and

FIG. 3 is a X-ray powder diffraction pattern of a rimsulfuron.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

It has been found that the present crystal form A of rimsulfuron has asignificant increase in its solubility and decrease in its viscosity,which significantly reduces the residue contamination and improve sprayequipment clean-out properties. In addition, it has been found that thecrystal form A of rimsulfuron is easier to be comminuted or groundcompared to amorphous rimsulfuron prepared in accordance with thedisclosure of EP0341011 A1. This allows the preparation of commercialformulations such as suspension concentrates (SC), oil-based suspensionconcentrates (OD), water-dispersible granules (WG) and water-solublegranules (SG). Hence, it is possible to prepare any formulations ofrimsulfuron in crystal form A, which is disclosed hereinafter.

By virtue of its high solubility and low viscosity, the crystal form Aof rimsulfuron is highly suitable for preparing compositions forcontrolling undesirable weeds.

According to a first aspect of the present invention a crystal form A ofrimsulfuron is provided, exhibiting at least 3 of the following reflexesas 2θ values in an X-ray powder diffractogram recorded using Cu—Kαradiation at 25° C.:

2θ=10.868±0.2   (1)

2θ=12.248±0.2   (2)

2θ=12.845±0.2   (³)

2θ=14.249±0.2   (4)

2θ=15.039±0.2   (⁵)

2θ=16.120±0.2   (6)

2θ=17.434±0.2   (⁷)

2θ=18.010±0.2   (⁸)

2θ=19.699±0.2   (⁹)

2θ=21.801±0.2   (10)

2θ=22.568±0.2   (11)

2θ=26.567±0.2   (12).

The crystal form A of rimsulfuron of an embodiment of the presentinvention is characterized by an X-ray powder diffractogram having atleast three of the reflexes indicated above. Preferably, the crystalform A is one having at least four of the aforementioned reflexes, morepreferably at least five, six or seven, or eight of said reflexes. AnX-ray powder diffractogram of the crystal form A of rimsulfuron is shownin FIG. 1, which will be described in detail hereinafter.

According to a preferred embodiment the crystalline form A exhibits atleast 3, 4, or 5 or all of the reflexes from the following:

θ=10.868±0.2   (1)

2θ=12.248±0.2   (2)

2θ=12.845±0.2   (³)

2θ=16.120±0.2   (6)

2θ=21.801±0.2   (10)

2θ=26.567±0.2   (12)

The crystal form A of rimsulfuron according to an embodiment of thepresent invention may be further characterized by Infrared (IR)spectroscopy. The IR spectrum of the crystal form A is shown in FIG. 2with characteristic bands at 3257.17 cm⁻¹ and 2943.91 cm⁻¹.

All IR spectra were obtained using the following acquisition parameters:

FT-IR spectrometer Bruker Tensor37 Diamond ATR unit from SpecacWavelength range 550-4000 cm⁻¹ Resolution 4 cm⁻¹ Number of scans 16

Methods for preparing amorphous rimsulfuron are well known in the art.Amorphous rimsulfuron is manufactured and available on a commercialscale. A particularly suitable method for preparing amorphousrimsulfuron is described in EP0341011 A1.

According to an embodiment of the present invention, the crystal form Aof rimsulfuron can be obtained by the processes below:

Rimsulfuron in an amorphous state is dissolved and then crystallizedfrom a solvent.

In one aspect, the present invention provides a process for preparing acrystal form A of rimsulfuron comprising steps of:

i) preparing a solution of an amorphous rimsulfuron in a solvent;

ii) effecting crystallization of rimsulfuron from the solution to obtaina solid precipitate; and

iii) isolating the solid precipitate.

Suitable solvents for preparing rimsulfuron crystal form A includehalogenated hydrocarbons (for example, chlorobenzene, bromobenzene,dichlorobenzene, chlorotoluene and trichlorobenzene), ethers (forexample, ethyl propyl ether, n-butyl ether, anisole, phenetole,cyclohexyl methyl ether, dimethyl ether, diethyl ether, dimethyl glycol,diphenyl ether, dipropyl ether, diisopropyl ether, di-n-butyl ether,diisobutyl ether, diisoamyl ether, ethylene glycol dimethyl ether,isopropyl ethyl ether, methyl tert-butyl ether, tetrahydrofuran,methyltetrahydrofuran, dioxane, dichlorodiethyl ether,methyl-tetrahydrofuran, polyethers of ethylene oxide and/or propyleneoxide), nitrated hydrocarbons (for example, nitromethane, nitroethane,nitropropane, nitrobenzene, chloronitrobenzene and o-nitrotoluene),aliphatic, cycloaliphatic or aromatic hydrocarbons (for example,pentane, n-hexane, n-heptane, n-octane, nonane), cymene, petroleumfractions within a boiling range of from 70° C. to 190° C., cyclohexane,methylcyclohexane, petroleum ether, ligroin, octane, benzene, tolueneand xylene), esters (for example, malonates, acetic acid n-butyl ester(n-butyl acetate), methyl acetate, ethyl acetate, isobutyl acetate,dimethyl carbonate, diethyl carbonate, dibutyl carbonate and ethylenecarbonate), and aliphatic alcohols (for example, methanol, ethanol,n-propanol, isopropanol, n-butanol and tert-amyl alcohol).

Preferred solvents are ethers, aromatic hydrocarbons (such as benzene,toluene, xylene, chlorobenzene), esters and aliphatic alcohols andmixtures thereof. Particularly preferred solvents or solvent mixturesare isopropanol, toluene, methyl-tetrahydrofuran, diethyl carbonate,chlorobenzene, n-butyl acetate, isobutyl acetate, n-butanol, ethanol,ethyl malonate, methyl t-butyl ether, and mixtures of toluene andbutanol, toluene and n-butyl acetate, ethyl malonate and methyl t-butylether, as well as butyl acetate and methyl t-butyl ether. Solventmixtures of more than 2 or 3 or 4 components are also envisaged by anembodiment of the present invention.

In an embodiment of the present invention, it is preferred that thesolvent comprises at least one alcohol, more preferably comprises atleast one straight or branched C₁-C₈ aliphatic alcohol, more preferablyat least one straight or branched C₁-C₄ aliphatic alcohol, even morepreferably methanol and ethanol.

According to another preferred embodiment the solvent essentiallyconsists of an alcohol as mentioned above or mixtures thereof.

Hence, according to a preferred embodiment in step (i), amorphousrimsulfuron is dissolved in a solvent comprising an alcohol. In apreferred embodiment, the solvent essentially consists of methanoland/or ethanol.

In step (ii) of the process, rimsulfuron is crystallized from thesolution. Techniques for effecting crystallization of rimsulfuron fromthe solution are known to those skilled in the art. For example, in anembodiment, where the solution in step (i) is formed at elevatedtemperatures, crystallization may be effected by cooling the solution toroom or ambient temperature. In one preferred embodiment,crystallization is effected by concentrating the solution formed in step(i) of the process. Alternatively, or in addition thereto, seedcrystals, in particular seed crystals of the aforementioned crystal formA of rimsulfuron, may be added to the solution formed in step (i), tofacilitate and/or enhance crystallization.

It is preferred that the solid precipitate of rimsulfuron recoveredduring the crystallization stage is washed with a solvent one or moretimes. Preferably, the solvent employed in the washing stage consists ofone or more components of the solvent employed for forming the solutionin step (i), as described hereinbefore. Alcohols, preferably methanoland ethanol, are particularly suitable solvents for washing therecovered solid of rimsulfuron.

The invention also relates to a composition comprising the crystal formA of rimsulfuron. The amount of the crystal form A of rimsulfuron isless than 75% by weight of the composition, preferably less than 50% byweight of the composition, more preferably less than 30% by weight ofthe composition, still more preferably about 25% by weight of thecomposition.

The use of rimsulfuron as a herbicide is well known in the art and isused on a commercial scale. The crystal form A of rimsulfuron is alsoactive in controlling unwanted plant growth, such as weeds. Techniquesof formulating and applying rimsulfuron are known in the art, forexample as disclosed in the prior art documents discussed hereinbefore.Rimsulfuron in the crystal form A of an embodiment of the presentinvention may be formulated and applied in an analogous manner.

Accordingly, in a further aspect, the present invention provides aherbicidal composition comprising rimsulfuron in the crystal form A asdefined hereinbefore.

Accordingly, an embodiment of the present invention furthermore providesprocesses for preparing compositions for controlling unwanted plantgrowth using the crystal form A of rimsulfuron.

The crystal form A of rimsulfuron can be incorporated in a known mannerto the customary formulations, such as suspension concentrates (SC),oil-based suspension concentrates (OD), water-soluble granules (SG),dispersible concentrates (DC), emulsifiable concentrates (EC), emulsionseed dressings, suspension seed dressings, granules (GR), microgranules(MG), suspoemulsions (SE) and water-dispersible granules (WG) usingsuitable auxiliaries, carriers and solvents.

In this context, the crystal form A of rimsulfuron may be present in aconcentration of from about 0.1 to about 50% by weight of the totalmixture, i.e., in amounts sufficient to achieve the required dosage. Theformulations are prepared, for example, by extending the crystal form Aof rimsulfuron with water, solvents and carriers, using, if appropriate,emulsifiers and/or dispersants, and/or other auxiliaries.

These formulations are prepared in a known manner by mixing the crystalform A of rimsulfuron with customary additives, for example, liquiddiluents, solid diluents, wetting agents, dispersants, thickening agentsand other formulation ingredients.

Liquid diluents include, but are not limited to, water,N,N-dimethylmamide, dimethyl sulfoxide, N-alkylpyrrolidone, ethyleneglycol, polypropylene glycol, propylene carbonate, dibasic esters,paraffines, alkylbenzenes, alkyl naphthalenes, glycerine, triacetine,oils of olive, castor, linseed, sesame, corn, peanut, cotton-seed,soybean, rape-seed and coconut, ketones such as cyclohexanone,2-heptanone, isophorone and 4-hydroxy-4-methyl-2-pentanone, acetatessuch as hexyl acetate, heptyl acetate and octyl acetate, and alcoholssuch methanol, cyclohexanol, decanol, benzyl and tetrahydrofurfurylalcohol.

Solid diluents can be water-soluble or water-insoluble. Water-solublesolid diluents include, but are not limited to, salts such as alkalimetal phosphates (e.g., sodium dihydrogen phosphate), alkaline earthphosphates, sulfates of sodium, potassium, magnesium and zinc, sodiumand potassium chloride, sodium acetate, sodium carbonate and sodiumbenzoate, and sugars and sugar derivatives such as sorbitol, lactose,sucrose and mannitol. Examples of water-insoluble solid diluentsinclude, but are not limited to clays, synthetic and diatomaceoussilicas, calcium and magnesium silicates, titanium dioxide, aluminum,calcium and zinc oxide.

Wetting agents include, but are not limited to, alkyl sulfosuccinates,laureates, alkyl sulfates, phosphate esters, acetylenic diols,ethoxyfluornated alcohols, ethoxylated silicones, alkyl phenolethyoxylates, benzene sulfonates, alkyl-substituted benzene sulfonates,alkyl a-olefin sulfonates, naphthalene sulfonates, alkyl-substitutednapthalene sulfonates, condensates of naphthalene sulfonates andalkyl-substituted naphthalene sulfonates with formaldehyde, and alcoholethoxylates. Alkyl naphthalene sulphonates, sodium salts areparticularly useful for the composition of an embodiment of theinvention

Dispersants include, but are not limited to, sodium, calcium andammonium salts of ligninsulfonates (optionally polyethoxylated); sodiumand ammonium salts of maleic anhydride copolymers; sodium salts ofcondensed phenolsulfonic acid; and naphthalene sulfonate-formaldehydecondensates. Of note are compositions comprising up to 10% by weight ofdispersant. Ligninsulfonates such as sodium ligninsulfonates areparticularly useful for the composition of an embodiment of theinvention. Naphthalene sulfonate-formaldehyde condensates such asNaphthalenesulfonic acid, polymers with formaldehyde, and sodium saltsare particularly useful for the composition of an embodiment of theinvention

Thickening agents include, but are not limited to, guar gum, pectin,casein, carrageenan, xanthan gum, alginates, methylcellulose,hydroxyethyl cellulose, hydroxypropylcellulose, andcarboxymethylcellulose. Synthetic thickeners include derivatives of theformer categories, and also polyvinyl alcohols, polyacrylamides,polyvinylpyrrolidones, various polyethers, their copolymers as well aspolyacrylic acids and their salts. Alkylpolyvinylpyrrolidones areparticularly useful for the composition of an embodiment of theinvention.

Other formulation ingredients can also be used in an embodiment of thepresent invention, such as dyes, defoamers, drying agents, and the like.These ingredients are known to one skilled in the art.

The crystal form A of rimsulfuron according to an embodiment of theinvention can be present in formulations and in its use forms, preparedfrom these formulations, and as a mixture with other active compounds(such as insecticides, attractants, sterilizing agents, bactericides,acaricides, nematicides, fungicides, growth-regulating substances,herbicides, safeners, fertilizers and semiochemicals) or with agents forimproving plant properties.

When used as a herbicide, the crystal form A of rimsulfuron according toan embodiment of the invention can furthermore be present informulations and its use forms, prepared from these formulations, and asa mixture with inhibitors which reduce degradation of the activecompounds after their use in the environment of the plant, on thesurface of plant parts or in plant tissues.

All plants and plant parts can be treated in accordance with anembodiment of the present invention. In the present context, plants areto be understood as meaning all plants and plant populations such asdesired and undesired wild plants or crop plants (including naturallyoccurring crop plants). Crop plants can be plants which can be obtainedby conventional breeding and optimization methods, by biotechnologicaland genetic engineering methods, or by combinations of these methods,including the transgenic plants and the plant cultivars which can orcannot be protected by plant breeders' rights. Plant parts are to beunderstood as meaning all parts and organs of plants above and below theground, such as shoot, leaves, needles, stalks, stems, flowers, fruitbodies, fruits, seeds, roots, tubers and rhizomes. Harvested materials,and vegetative and generative propagation materials, for example,cutting, tubers, meristem tissue, rhizomes, offsets, seeds, single andmultiple plant cells and any other plant tissues, are also included.

As used herein, the term “about,” when used in connection with anumerical amount or range, means somewhat more or somewhat less than thestated numerical amount or range, to a deviation of ±10% of the statednumerical amount or endpoint of the range.

“Surrounding,” as used herein, refers to the place on which the plantsare growing, the place on which the plant propagation materials of theplants are sown or the place on which the plant propagation materials ofthe plants will be sown.

Treatment according to examples of the present invention of the plantsand plant parts with the compositions or formulations of examples of theinventions is carried out directly or by allowing the compositions orformulations to act on their surroundings, habitat or storage space bythe customary treatment methods. Examples of these customary treatmentmethods include dipping, spraying, vaporizing, fogging, broadcasting,painting on in the case of propagation material, and applying one ormore coats particularly in the case of seed.

The compositions or formulations of embodiments of the present inventionmay be used to control dicotyledonous weeds, such as Abutilon spp.,Ambrosia spp., Amaranthus spp., Chenopodium spp., Erysimum spp.,Euphorbia spp., Fallopia spp., Galium spp., Hydrocotyle spp., Ipomoeaspp., Lamium spp., Medicago spp., Oxalis spp., Plantago spp., Polygonumspp., Richardia spp., Sida spp., Sinapis spp., Solarium spp., Stellariaspp., Taraxacum spp., Trifolium spp., Veronica spp., Viola spp. andXanthium spp.

The compositions or formulations of embodiments of the present inventionmay also be used to control monocotyledonous weeds, such as Agrostisspp., Alopecurus spp., Apera spp., Avena spp., Brachiaria spp., Bromusspp., Digitaria spp., Echinochloa spp., Eleusine spp., Eriochloa spp.,Leptochloa spp., Lolium spp., Ottochloa spp., Panicum spp.,Paspalumspp., Phalaris spp., Poa spp., Rottboellia spp., Setaria spp., Sorghumspp., both intrinsically sensitive as well as resistant (e.g. ACCaseand/or ALS resistant) biotypes of any of these grass weeds, as well asbroadleaf monocotyledonous weeds such as Commelina spp., Monochoriaspp., Sagittaria spp. and sedges such as Cyperus spp. and Scirpus spp.

The benefits of the present invention are seen most when the herbicidalcomposition is applied to kill weeds in growing crops of useful plants,such as maize (corn) including field corns, pop corns and sweet corns,cotton, wheat, rice, oats, potatoes, sugar beets, plantation crops (suchas bananas, fruit trees, rubber trees, tree nurseries), vines,asparagus, bushberries (such as blueberries), caneberries, cranberries,flax, grain sorghum, okra, peppermint, rhubarb, spearmint and sugarcane.According to aspects of the present invention, maize and potatoes aremore concerned.

Embodiments of the present invention will now be described by way of thefollowing examples, which are provided for illustrative purposes only,and not intended to limit the scope of the disclosure.

All percentages are given in weight % unless otherwise indicated.

EXAMPLES Example 1 Preparation of Amorphous Rimsulfuron in Accordancewith the Disclosure of EP0341011 A1

To a stirred suspension of 0.60 g (0.0024 mol) of3-ethylsulfonyl-2-pyridinesulfonamide and 0.90 g (0.0034 mol) of phenyl(4,6-dimethoxypyrimidin-2-yl)carbamate in 5 ml acetonitrile, 0.52 g(0.0034 mol) of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) was added andstirred for 15 minutes. The solution was diluted with water andacidified with hydrochloric acid. The resulting solid precipitate wascollected and washed with water and ether to give 0.70 g (70%) of thetitle compound: melting point of 160° C.-162° C.

As shown in FIG. 3, the X-ray powder diffraction pattern of theresulting rimsulfuron product has no significant signals, whichindicates the rimsulfuron product prepared in accordance with thedisclosure of EP0341011 A1 is amorphous.

Example 2 Preparation of the Crystal Form A of Rimsulfuron

Crystallization from Methanol

10 ml methanol was charged into the reactor to dissolve cruderimsulfuron prepared in example 1 under stirring. This process lastedfor 2 hours under room temperature, and white solid precipitateappeared. The mixture was then cooled down to 0° C.-5° C. and maintainedfor 1 hour to allow complete crystallization. After that, the mixturewas centrifuged. The filter cake was washed with methanol. The resultingsolid was dried under high vacuum to give crystals of pure rimsulfurontechnical (Purity: 98%).

The crystals were characterized as being of the crystal form A ofrimsulfuron using both IR spectrometry and X-ray powder diffraction.

The IR spectrum of the crystal form A of rimsulfuron is set out in FIG.2. The IR spectrum exhibits characteristic peaks at 3257.17 cm⁻¹ and2943.91 cm⁻¹.

The crystal form A of rimsulfuron has the X-ray powder diffractogramshown in FIG. 1 with the reflexes listed in Table 1 below.

TABLE 1 Crystal Form A 2 θ (°) d (Å) 10.868 ± 0.2 8.14 ± 0.05 12.248 ±0.2 7.23 ± 0.05 12.845 ± 0.2 6.89 ± 0.05 14.249 ± 0.2 6.22 ± 0.05 15.039± 0.2 6.12 ± 0.05 16.120 ± 0.2 5.50 ± 0.05 17.434 ± 0.2 5.09 ± 0.0518.010 ± 0.2 4.93 ± 0.05 19.699 ± 0.2 4.51 ± 0.05 21.801 ± 0.2 4.08 ±0.05 22.568 ± 0.2 3.94 ± 0.05 26.567 ± 0.2 3.56 ± 0.05

Example 3 Preparation of the Crystal Form A of Rimsulfuron

Crystallization from Ethanol

10 ml ethanol was charged into the reactor to dissolve crude rimsulfuronprepared in example 1 under stirring. This process lasted for 2 hoursunder room temperature, and white solid precipitate appeared. Themixture was then cooled down to 0° C.-5° C. and maintained for 1 hour toallow complete crystallization. After that, the mixture was centrifuged.The filter cake was washed with some ethanol. The resulting solid wasdried under high vacuum to give crystals of pure rimsulfuron technical(Purity: 98%).

The crystals were characterized as being the crystal form A ofrimsulfuron using IR spectrometry and X-ray powder diffraction asdescribed in Example 2.

Example 4 Preparation of Oil Based Suspension Concentrate (OD)Formulation

All the components listed in Table 2 below were mixed uniformly andground with a Dyno-Mill (manufactured by Willy A. Bachofen AG) to obtainan oil based suspension concentrate.

TABLE 2 Ingredients Weights % Function Rimsulfuron, crystal form A, 40.80 Active compound 98%, prepared in Example 2 Amorphous Rimsulfuron, 040.8 Active compound prepared in Example 1 Sodium lignosulfonate 22 22Dispersing agent (REAX ® 88B) Alkylpolyvinylpyrrolidone 20 20 Thickeningagent Corn oil Balance Balance Carrier to 100% to 100%

Example 5 Preparation of Soluble Granules (SG)

All the components listed in Table 3 below were mixed, blended andmilled in a high-speed rotary mill. Sufficient water was added to obtainan extrudable paste. The paste was extruded through a die or screen toform an extrudate. The wet extrudate was dried at 70° C. in a vacuumoven and then sifted through 0.71 mm -2 mm screens to obtain the productgranules.

TABLE 3 Ingredients Weights % Function Rimsulfuron, crystal form A,25.51 0 Active compound 98%, prepared in Example 2 AmorphousRimsulfuron, 0 25.51 Active compound prepared in Example 1 Lignosulfonicacid, sodium 15 15 Dispersing agent salt, (REAX ® 88B)Naphthalenesulfonic acid, 6 6 Dispersing agent polymer withformaldehyde, sodium salt (TAMOL ® NN 8906) Sodium acetate 4 4 FillerSodium carbonate 4 4 Filler Non-ionic aqueous emulsion 1 1 Antiform ofPolydimethylsiloxanes Mannitol Balance Balance carrier to 100% to 100%

Example 6 Preparation of Water Dispersible Granules (WG)

All the components listed in Table 4 below were mixed, blended andmilled in a high-speed rotary mill. Sufficient water were added toobtain an extrudable paste. The paste was extruded through a die orscreen to form an extrudate. The wet extrudate was dried at 70° C. in avacuum oven and then sifted through 0.71 mm-2 mm screens to obtain theproduct granules.

TABLE 4 Ingredients Weights % Function Rimsulfuron, crystal form A,25.51 0 Active compound 98%, prepared in Example 2 AmorphousRimsulfuron, 0 25.51 Active compound prepared in Example 1 Alkylnaphthalene 2 2 Wetting agent sulphonate, sodium salt (Akzo Nobel)Lignosulfonic acid, sodium 15 15 Dispersing agent salt, REAX ® 88B)Naphthalenesulfonic acid, 6 6 Dispersing agent polymer withformaldehyde, sodium salt (TAMOL ® NN8906) Sucrose 10 10 FillerNon-ionic aqueous emulsion 1 1 Antiform of PolydimethylsiloxanesMannitol Balance Balance Carrier to 100% to 100%

Example 7 Determining Water Solubility

A stock pH 7 buffer solution was prepared by adding aqueous sodiumhydroxide solution (0.1 M, 145 mL) to aqueous potassium dihydrogenphosphate solution (0.1 M, 250 mL), and then adding sufficient distilledwater to adjust the final volume to 500 mL. At least 1 time and up toabout 5 times the amount of rimsulfruon needed for saturation was addedto a mixing vessel containing stock buffer solution at the testtemperature (e.g., 20° C.). The mixture was magnetically stirred in thedark while being maintained at the test temperature. Samples wereperiodically removed for analysis. The samples were centrifuged using ahigh speed, temperature-controlled centrifuge at the test temperaturefor about 20 minutes at ≧12000 G to remove suspended particles. Analiquot of each supernatant was taken for analysis.

The concentration of rimsulfuron in the supernatant was determined by ahigh pressure liquid chromatography (HPLC) with a reversed phasechromatography column and UV detection. The method should includedevelopment of best-fit calibration curves based on at least threestandards using linear regression analysis Samples were successivelywithdrawn from the mixing vessel and analyzed until three successivesamples show little or no variation in concentration. The test ispreferably replicated to ensure accuracy.

TABLE 5 Original Concentration concen- measured by Formu- tration, HPLCafter Sample lation % treatment, % Solubility Rimsulfuron, crystal OD 4035   88% form A, 98%, prepared in Example 2 Amorphous OD 40 14   35%Rimsulfuron, prepared in Example 1 Rimsulfuron, crystal SG 25 24.9 99.6%form A, 98%, prepared in Example 2 Amorphous SG 25 15   60% Rimsulfuron,prepared in Example 1 Rimsulfuron, crystal WG 25 23   92% form A, 98%,prepared in Example 2 Amorphous WG 25 12   48% Rimsulfuron, prepared inExample 1

Example 8 Cleanout Test

The cleanout test was conducted by dispersing in water a sample toproduce a concentration that is normally used when applying theherbicide: 25% rimsulfuron. The sample was added to tap water (300 mL)in a 400 mL beaker and magnetically stirred for 2 minutes. The mixturewas then stirred for 2 minutes, whereupon the resulting dispersion wasdispensed in three 100 mL aliquots to 4-oz (118 mL) polyethylenebottles. The bottles were capped, inverted twice and allowed to standovernight.

After standing overnight, each individual bottle was inverted twice andthe liquid contents were then poured out. Tap water (10 mL) was addedand the bottle was inverted until all sediment was re-suspended,whereupon the contents were poured out. Tap water (100 mL) was added andthe bottle was inverted twice and then allowed to stand undisturbed for10 minutes. The bottle was inverted twice more and the contents werepoured out. Acetonitrile (10 mL) was added to the bottle to extract anyremaining material. The acetonitrile solution was analyzed byreversed-phase liquid chromatography with UV detection. The cleanoutrating (the concentration of rimsulfuron herbicide in the acetonitrilesolution) is reported in % in Table 6 below. Lower cleanout ratingsindicate more effective cleanout compared to higher ratings.

TABLE 6 Cleanout Sample Formulation rating, % Rimsulfuron, crystal formA, 98%, OD 5 prepared in Example 2 Amorphous Rimsulfuron, prepared OD 26in Example 1 Rimsulfuron, crystal form A, 98%, SG 0.1 prepared inExample 2 Amorphous Rimsulfuron, prepared SG 10 in Example 1Rimsulfuron, crystal form A, 98%, WG 2 prepared in Example 2 AmorphousRimsulfuron, prepared WG 13 in Example 1

The results in Table 6 demonstrate that the crystal form A ofrimsulfuron exhibited markedly superior cleanout properties that theknown amorphous rimsulfuron product.

1. A crystal form A of rimsulfuron, exhibiting at least 3 of thefollowing reflexes in an X-ray powder diffractogram recorded using Cu—Kαradiation at 25° C.:2θ=10.868±0.2   (1)2θ=12.248±0.2   (2)2θ=12.845±0.2   (³)2θ=14.249±0.2   (4)2θ=15.039±0.2   (⁵)2θ=16.120±0.2   (6)2θ=17.434±0.2   (⁷)2θ=18.010±0.2   (⁸)2θ=19.699±0.2   (⁹)2θ=21.801±0.2   (10)2θ=22.568±0.2   (11)2θ=26.567±0.2   (12).
 2. The crystal form A of rimsulfuron according toclaim 1, exhibiting at least 3 of the following reflexes in an X-raypowder diffractogram recorded using Cu—Kα radiation at 25° C.:2θ=10.868±0.2   (1)2θ=12.248±0.2   (2)2θ=12.845±0.2   (³)2θ=16.120±0.2   (6)2θ=21.801±0.2   (10)2θ=26.567±0.2   (12).
 3. The crystal form A of rimsulfruon accordingclaim 1 exhibiting at least four of the said reflexes.
 4. The crystalform A of rimsulfuron according to claim 1 exhibiting at least five ofthe said reflexes.
 5. The crystal form A of rimsulfuron according toclaim 1, exhibiting IR spectrum with the characteristic bands at 3257.17cm⁻¹ and 2943.91 cm⁻¹.
 6. A process for the preparation of a crystalform A of rimsulfuron according to claim 1, the process comprising: i)preparing a solution of an amorphous rimsulfuron in a solvent; ii)effecting crystallization of rimsulfuron from the solution to obtain asolid precipitate; and iii) isolating the solid precipitate.
 7. Theprocess according to claim 6, wherein the solvent comprises an alcohol.8. The process according to claim 6, wherein the solvent is methanoland/or ethanol
 9. A composition comprising the crystal form A ofrimsulfuron according to claim 1 and at least one auxiliary.
 10. Thecomposition according to claim 9, in the form of a suspensionconcentrate (SC), an oil-based suspension concentrate (OD),water-soluble granules (SG), a dispersible concentrate (DC), anemulsifiable concentrate (EC), an emulsion seed dressing, a suspensionseed dressing, granules (GR), microgranules (MG), a suspoemulsion (SE)or water-dispersible granules (WG).
 11. The composition according toclaim 9, wherein the auxiliary is selected from one or more of asolvent, a diluent, a wetting agent, a dispersant, and a thickener. 12.The composition according to claim 9, which comprises crystal form A ofrimsulfuron in an amount of less than 75% by weight.
 13. A method forcontrolling unwanted plant growth, comprising applying to the plant,plant part, or surroundings of the plant, a herbicidal effective amountof a crystal form A of rimsulfuron according to claim
 1. 15. A processfor preparing crystal form A of rimusulfuron according to claim
 1. 16. Acomposition comprising crystal form A of rimusulfuron according to claim1.